1. Field of the Invention
This invention relates to a recording material to be used for image forming device such as electrophotographic device or electrostatic recording device. Particularly, it relates to a sheet which is the recording material which can be used for the above device for detecting the running situation and presence of the recording material within the device by an optical means, and to an image forming device by use of the sheet.
2. Related Background Art
In the prior art, as the recording material of this kind, there is, for example, a transparent polyethylene terephthalate (PET) film sheet provided for overhead projector (OHP). In an electrophotographic device which passes such PET film sheet as the recording material, for detection of an accident such as paper jamming, etc., for example, a light from a light source is irradiated on the recording material, and presence of the reflected light or presence of the transmitted light is detected by provision of an optical detection means for improving the detection precision or accuracy.
Whereas, a PET sheet permits the light to transmit therethrough and detection with an optical detection means is hardly possible, and therefore various proposals have been made about improvements of the recording material in order to improve the detection precision. For example, Japanese Patent Application Laid-open No. 58-106550 proposes to provide a peelable opaque member at the end of a transparent film. Also, Japanese Patent Application Laid-open No. 58-105157 proposes formation of a coated layer with an opaqueness of 60% or more according to JIS P-8138 in order to sheild the visible light, and further Japanese Patent Application Laid-open No. 59-7367 one having a metal vapor deposited on the whole sheet in order to shield IR-ray.
However, in the case of the prior arts as described above, for example, in the case of providing an opaque member, there was a fear that the recording materials may be obstructed within the electrophotographic device during paper passage due to the stepped difference of the opaque member, or the toner image of the unfixed portion may be disturbed by the paper passage shock by the stepped difference portion. On the other hand, the coating layer for shielding visible light is poor in shielding characteristic against the light of IR level from an LED light source conventionally used as inexpensive light soruce, and the detection time of the signal becomes shorter in the case of further narrower coating width, whereby detection precision with be lowered.
Further, according to metal vapor deposition on the whole sheet, visible light transmittance of the film itself becomes lower, and when it is provided for OHP as the transmissive image, the image will become dark, and moreover, there was a drawback that vapor deposition by use of a vacuum device resulted in increased cost of the film itself.
On the other hand, the transmission type detection means has the light source and the photosensor arranged with an interval apart from each other, whereby the positional precision can be guranteed with difficulty, and also due to unstable detection precision, there have been made proposals to enhance reliability by using a detection means of the reflection type of higher precision, or by using separately the both within one device. However, there existed no transfer material such as transparent sheet, etc. satisfying the both characteristics of reflection and transmission (shielding).